Process of retting fibrous substances



UNITED STATES PATENT OFFICE.

ERICK LUDVIG RINMAN, OF DJURSHOLM, SWEDEN.

PROCESS OF BETTING FIBROUS SUBSTANCES.

No Drawing.

' tion.

The present process of treating fibrous substances is applicable to all such substances which contain fibers capable of being spun. Thus it is possible'according to the present process in an advantageous and economical manner to treat not only such fibrous substances which have heretofore been treated by retting, but also other fibrous substances for which there have hitherto not existed any suitable methods of retting.

It has already been proposed, for the purpose of retting, to treat the fibrous substances with a diluted solution of potassium hydrate or sodium hydrate, but ithas not been possible to use the fibers thus obtained on account of the fibers being affected-by the alkali used. According to the present invention a lye from a previous treatment of vegetable substances with the said alkalis to which lye the necessary quantity of free alkali hydrate has been added, is always used as treating liquid, with or without the use of increased temperature and pressure.

It has been found that the fibers obtained in this manner become particularly good and serviceable, the presence of oxy compounds in such lyes reducing to a great ex tent the influence of the alkali on the fibers without preventing the extraction aimed at.

1.035 up to 1.1 may be used with advantage for producing a new treating liquid.

WVhen the treating liquid has been removed bywashing and after drying, if desired, the raw material thus treated is ready to be subjected to the usual mechanical treatment for obtaining fibers capable of being spun. The-process is most eflicient if the treatment is made in a hot state. \Vhen the treatment is made in a hot state the most suitable boiling liquid is a lye containing 0.2 to 2 per cent. by weight of sodium hydrate. The time of treatment may vary from one hour to a longer period. If the treatment is carried out at about 100 C. a time of treatment of about 8 to 5 hours is required. If higher temperatures, for inextracted organic substances.

make the present process really economical.

stance 135 (1, are used, the boiling time may be shortened to one to two hours: The use of artificial pressure also reduces the time of treatment.

During the treatment it is most advantageous to use lyes with a small percentage of alkali. This may of course be obtained in many ways. By allowing the treating liquid to pass from one treating. receptacle to another, or by causing the liquid to cir-. culate in other manner, it is possible to treat the raw material with a larger quantity of lye than that contained in the treating vessel. It is of course also possible during the treatment to supply-the necessary alkali gradually to the boiling liquid in such Specification of Letters Patent. I Patented J 29 1920 Application filed October 2, 1918. SeriaI No. 256,612.

manner that the liquid always contains the required quantity of free alkali hydrate.

The waste liquor obtained during these treatments contains the alkali usedand the In order to it is necessary to recover the alkali used, and, simultaneously, the extracted organic substances should be utilized for producing valuable products. This is preferably-at tained by dry distilling the waste liquors when suitably concentrated and. mixed with the required quantity of strong bases, for instance sodium hydrate and hydrate of lime, in the presence of superheated steam,

preferably in the marner previously disclosed in respect of'dry distillation of waste liquors from the sulfate cellulose manufacture. In this manner acetone, wood spirit,

higher alcohols, ketones, oils, and a con siderable quantity of wax, ammonia and amins are obtained. is used for preparing a new quantity of treating liquid. I

The recovered alkali The following may be given as an example of the application of the present process to the retting of flax. Bundles of.

flax freed from the seeds are mounted in a frame, preferably in vertical position. The frame with the flax is then introduced into the boiler, in which the flax is treated during about two hours at a temperature of about 135 C. with a waste liquor from a previous boiling having a specific gravity of about 1.074 and containing about from 0.2 to 1 per cent. Na O. A quantity of about lOO kg. Na,O is consumed for each ton of airdried flax, consequently, this quantity of soda lye must be present in the boilin lye or be added to the same, together wit an s quantity of about 10 percent. After boiling the lye is removed and washed with water. The Water remaining in retted flax may preferably be first pressed the remaining Water being evaporated sans of a current of hot air, or in other ole manner. claim:

e process of retting fibrous substances ch consists in treating the fibrous subtnces with a waste lye from a previous treatment of vegetable substances with alkali hydrate to which Waste lye free alkali hydrate has been added, and carrying out the treatment at a temperature of at least 90 C. and with. a treating liquid so concentrated that its specific gravity is at least 1.074 but the percentage of caustic alkali of which does not exceed 3 per cent. alkali hydrate.

ERIK LUDVIG RINMAN. 

